From the Guidelines
The color of nasal mucus alone cannot reliably predict whether someone is contagious. While clear mucus typically indicates allergies or non-infectious causes, and yellow or green mucus often suggests infection, this correlation isn't definitive for determining contagiousness. Many contagious respiratory infections can be spread before symptoms appear or when mucus is still clear. The color change to yellow or green happens when white blood cells fight an infection and release enzymes containing iron, which doesn't necessarily indicate whether the infection is viral or bacterial, nor its contagiousness.
According to the clinical practice guideline update for adult sinusitis 1, nasal purulence alone does not indicate a bacterial infection, and discolored nasal discharge is a sign of inflammation, not specific for infection. The coloration of nasal discharge is related to the presence of neutrophils, not bacteria.
Other factors like fever, duration of symptoms, and overall health status are more reliable indicators of contagiousness. If you're concerned about spreading illness, it's best to consider multiple symptoms together, practice good hygiene including frequent handwashing, cover coughs and sneezes, and stay home when feeling unwell regardless of mucus color. The most contagious period for many respiratory infections is often early in the illness, sometimes before noticeable mucus changes occur.
Some studies suggest that the presence of symptoms for at least seven days, persistent purulent nasal discharge with maxillary tooth or unilateral facial pain, and worsening symptoms after initial improvement may predict a higher likelihood of bacterial infection 1. However, these findings are not conclusive, and the diagnosis of bacterial sinusitis should be made based on a combination of clinical findings and patient history.
In terms of management, symptomatic treatment and reassurance are the preferred initial treatment strategy for patients with mild symptoms 1. Antibiotics may be considered for patients with severe symptoms, but the decision to prescribe antibiotics should be made on a case-by-case basis, taking into account the patient's overall health status and medical history.
Overall, while the color of nasal mucus may provide some clues about the presence of an infection, it is not a reliable indicator of contagiousness, and other factors should be considered when assessing the risk of transmission.
From the Research
Color of Nasal Mucus and Contagiousness
- The color of one's nasal mucus (snot) is not a reliable indicator of whether or not they are contagious 2, 3, 4.
- There is no direct correlation between the color of nasal mucus and the presence of a contagious infection.
- The provided studies focus on the treatment of upper respiratory infections, antibiotics, and the validation of outcome measures for rhinosinusitis, but do not address the relationship between nasal mucus color and contagiousness.
Upper Respiratory Infections
- Upper respiratory infections (URIs) are commonly caused by viruses, but some are caused by bacteria 2.
- Antibiotics are not effective against viral URIs, and their use can contribute to antibiotic resistance 3, 4.
- The treatment of URIs typically involves symptomatic relief, such as pain management and decongestants.
Nasal Mucus and Rhinosinusitis
- The SNOT-22 score is a validated measure of rhinosinusitis health status and quality of life 5, 6.
- The score can be stratified into mild, moderate, or severe categories, but this does not directly relate to the color of nasal mucus or contagiousness.
- The provided studies on SNOT-22 and SNOT-20 scores focus on the validation of these outcome measures for rhinosinusitis, but do not address the relationship between nasal mucus color and contagiousness.